> because not having it mandatory led to infection waves and in the army that's even worse than in genpop

It also makes a stupidly-obvious tactic viable for the enemy.

Specifically, there is a reason the US military still vaccinates for smallpox, a virus that was eradicated world-wide 50 years ago. As a civilian, you can't get it even if you wanted it, but as a soldier, you have to take it even if you don't want it.

There is also the legend of sieging cities by catapulting diseased cows over the city walls. And if anyone knows the citation for that story, I'd love to see it.

	▲	JumpCrisscross a day ago \| parent [-]
		"The earliest documented incident of the intention to use biological weapons is possibly recorded in Hittite texts of 1500–1200 BC, in which victims of tularemia were driven into enemy lands, causing an epidemic" [1]. Smallpox is a can of worms. But if you learn your enemy are idiots and don't have a flu vaccine, and you know your own forces do, I don't think you're going to get yourself sanctioned by your trade partners for exposing them to the flu. It will take out a statistically-measurable fraction of their troops, at a predictable interval, something you can plan to exploit with manoeuvre. [1] https://en.wikipedia.org/wiki/History_of_biological_warfare#...